The present invention relates to a stage apparatus and a charged particle beam apparatus, and particularly to a stage apparatus that specifies a stage position by irradiating beams on a reflecting mirror and a charged particle beam apparatus that includes the stage apparatus.
Along with miniaturization of semiconductor devices, high accuracy compatible with the miniaturization is required for not only manufacturing equipment but also inspection equipment and evaluation equipment. To evaluate patterns formed on a semiconductor wafer or inspect defects in a formed wafer, a scanning electron microscope (hereinafter, referred to as an SEM) is normally used and particularly, to evaluate a shape size of patterns, a critical dimension SEM is used.
The critical dimension SEM is a device that irradiates electron beams on a wafer, performs image processing on obtained secondary electron signals, determine an edge of a pattern from a change in light and darkness, and calculates sizes, etc. To observe and inspect the entire area of a wafer, on the critical dimension SEM, provided is an X-Y stage that is capable of positioning a desired portion of the wafer as an irradiation position of beams. In the X-Y stage, for example, a method in which the X-Y stage is driven by a rotation motor and ball screws, or a method in which the X-Y stage is driven by a linear motor is used. In addition, an X-Y stage may be used in which a rotary motion and the like are performed not only on an X-Y plane and but also on a Z axis or around the Z axis.
In the X-Y stage, for accurately performing positioning of wafers, it is necessary to perform detection of a stage position with high accuracy. For this purpose, known is a method in which a laser interferometer and a reflecting mirror are used.
A laser interferometer is capable of irradiating laser light on a reflecting mirror and detecting a stage position with a resolution of several tens of picometer order due to interference with reflected waves. Further, since measurement can be performed at the same height as that of a wafer, an Abbe error is minimized; therefore, a laser interferometer is widely used for position measurement in lots of precision stages including the critical dimension SEM.
In the critical dimension SEM, to cope with enlargement of wafers or diversification of wafer inspection means, a stroke of the X-Y stage is required to be increased. When wafers are observed by the wafer inspection means (for example, an optical microscope and the like) other than an SEM, a stroke of the X-Y stage is further required to be increased.
When the stroke of the X-Y stage is increased, elongation of the reflecting mirror is required with an increase in the stroke for reflecting laser light over the entire stroke. In this case, it is difficult to assure flatness of a plane of the reflecting mirror, and at the same time an increase in vibrations due to the elongation results in degradation of the measurement accuracy. Further, for assuring a motion space of the elongated reflecting mirror, a sampling chamber itself is required to be grown in size, and as a result it causes an increase in cost of manufacture and transportation and an enlargement of an installation area.
In JP2556361, disclosed is a technology of switching to a stage-positioning system using a length measurement system (for example, a linear scale) in which a size of a mirror is minimized and a mirror is not used other than a positioning range by laser light.